Controle microbiológico e atividade enzimática em compostagem de resíduos de poda de árvores e lodo de esgoto

Abstract

The objective of this work was to reuse the urban tree pruning and sewage sludge for composting. The addition of slaked lime and inocula to compost, both in laboratory and in the field, was investigated. The microbiological content, enzyme activities, temperature, pH and concentrations of carbon and nitrogen were determined. The standard counting of bacteria and fungi (yeasts and filamentous fungi) reached maximum values in the range of 1012 and 108 CFU/mL, respectively. Liming inhibited the total coliforms and fecal coliforms. In addition, Salmonellas and the four enzymes investigated were also inhibited when a 1:1 slaked lime to sewage sludge ratio was used. In the experiments in the field, the mass was not sanitized and was used slaked lime at 25 % w/w in relation to sewage sludge; the thermophilic phase occurred in a short period. The activities of cellulases, proteases, phenoloxidases and tannases reached the highest percentage in the active phase of waste degradation. The moisture in the composting field ranged from 55 to 65%. During the composting in the presence of slaked lime, pH reached alkaline values while in other treatments, pH was around neutrality. The final product showed a carbon: nitrogen ratio between 9 and 16 after 60 days of composting. The particle size of the urban pruning, the volume of waste in laboratory treatments and the presence of slaked lime influenced composting. The urban tree pruning and sewage sludge can be reused after the composting treatment for humus production, whose final product can be used in the recovery of soil